Papers by Gustaaf Hallegraeff
Research Square (Research Square), Oct 20, 2022
Antarctic diatom populations of Asteromphalus hookeri and related species such as A. hyalinus and... more Antarctic diatom populations of Asteromphalus hookeri and related species such as A. hyalinus and A. parvulus exhibit a highly variable number of hyaline rays ranging from 3 broad + 1 narrow (3 + 1) in the smallest valves, with 4 + 1 (27%) and 5 + 1 rays (35%) most common, and 6 + 1, 7 + 1, and rarely 8 + 1 rays only in larger cells. During December 1959 to April 1960 in the southern sector of the Atlantic Ocean, 6% of valves occurred as "double forms" with epitheca and hypotheca of the same cell exhibiting 4 + 1/3 + 1, 5 + 1/4 + 1, 6 + 1/5 + 1 and 7 + 1/6 + 1 ray combinations. Smaller cells (3 + 1, 4 + 1) always exhibited jagged separation lines in the central area, but larger cells (7 + 1, 8 + 1) had mostly smooth lines, and either jagged or smooth separation lines occurred in intermediate 5 + 1 and 6 + 1 forms, respectively. Epitheca and hypotheca of one and the same cell always exhibited jagged or smooth separation lines, but never mixtures. Observations of silica deposition during October to November 2011 around the Kerguelen Island plateau using the PDMPO uorescent marker suggest that Asteromphalus separation lines play a key role in silica cell wall development. We discuss implications for taxonomy and our understanding of ecophysiology of what we designate as two highly variable and often confused and overlapping diatom taxa, A.
Journal of AOAC International, May 1, 2020
Background Paralytic shellfish toxins (PST) are a significant problem for the Tasmanian shellfish... more Background Paralytic shellfish toxins (PST) are a significant problem for the Tasmanian shellfish and Southern Rock Lobster (Jasus edwardsii) industries, and the introduction of a rapid screening test in the monitoring program could save time and money. Objective The aim was to perform a single-laboratory validation of the Neogen rapid test for PST in the hepatopancreas of Southern Rock Lobster. Methods The AOAC INTERNATIONAL guidelines for the validation of qualitative binary chemistry methods were followed. Three different PST profiles (mixtures) were used, of which two were commonly found in naturally contaminated lobster hepatopancreas (high in gonyautoxin 2&3 and saxitoxin), and the third toxin profile was observed in a few select animals (high in gonyautoxin 1&4). Results The Neogen test consistently returned negative results for non-target toxins (selectivity). The probability of detection (POD) of PST in the lobster hepatopancreas using the Neogen test increased with increasing PST concentrations. POD values of 1.0 were obtained at ≥0.57 mg STX-diHCl eq/kg in mixtures 1 and 2, and 0.95 and 1.0 for mixture 3 at 0.79 and 1.21 mg STX-diHCl eq/kg, respectively, with a fitted POD of 0.98 for 0.80 mg STX-diHCl eq/kg. The performance of the Neogen test when using four different production lots (ruggedness) showed no significant differences. Conclusions The results of the validation study were satisfactory and the Neogen test is being trialed within the Tasmanian PST monitoring program of Southern Rock Lobster. Highlights The Neogen rapid kit was successfully validated for the detection of PST in Southern Rock Lobster hepatopancreas.
Zenodo (CERN European Organization for Nuclear Research), Aug 21, 2022
The Tasmanian Southern Rock Lobster (Jasus edwardsii) fishery has been challenged by recurrent di... more The Tasmanian Southern Rock Lobster (Jasus edwardsii) fishery has been challenged by recurrent dinoflagellate blooms of Alexandrium catenella since 2012. The initial bloom resulted in the first ever closure of an Australian lobster fishery due to marine biotoxins and exposed several key knowledge gaps for managing food safety and market access risk. To fill these gaps, experimental studies were conducted to determine paralytic shellfish toxin (PST) toxicokinetics. Adult male lobsters fed highly toxic mussels (6 mg STX.2HCl eq kg-1) accumulated PST in the hepatopancreas at an exponential rate of 6% per day, reaching a maximum level of 9 mg STX.2HCl eq kg-1 in three weeks. However, lobsters exposed to toxic algae culture suspensions at 2 x 10 5 cells L-1 did not accumulate any toxin. Neither accumulation of PST nor exposure to toxic cells resulted in any gross impact on the health of lobsters, as assessed by a comprehensive range of behavioural, immune, nutritional and biochemical indicators. Field studies over a period of eight years confirmed the ability of lobster hepatopancreas to rapidly accumulate and depurate toxins in the wild, with a high degree of variability. Analysis of 496 hepatopancreas samples collected during A. catenella blooms identified high risk sites and seasons; demonstrated the usefulness of mussels as sentinel species for indicating PST risk; and enabled quantification of the confidence level associated with current risk management sampling practices. The combined experimental and field results have led to improved risk management for this AUD 97M wild fishery.
Harmful Algae, 2014
Pinnatoxins are members of the toxic cyclic imine group and were first characterized over two dec... more Pinnatoxins are members of the toxic cyclic imine group and were first characterized over two decades ago. However, the dinoflagellate producer of pinnatoxins was not known until 2011 when cultured from sediment samples in New Zealand. The causative species, Vulcanodinium rugosum Nezan & Chomerat, was described in 2011 from a bloom sample from a Mediterranean lagoon. V. rugosum has now been recorded around the world including Australia, New Zealand, Japan, China, Hawaii and Europe. V. rugosum strains of various origins produce different pinnatoxins and also differ from each other in partial large subunit rDNA and internal transcribed spacer regions suggesting the existence of a species complex. This study sought to determine the status of this species by combining DNA sequence data, morphological characteristics, mating experiments and toxin profiles from strains originating from five geographical locations.
Phycologia, Jul 1, 2013
Phytoplankton species with a cosmopolitan distribution are traditionally expected to show little ... more Phytoplankton species with a cosmopolitan distribution are traditionally expected to show little genetic differentiation given the lack of geographical barriers in the ocean. To gain an understanding of the genetic variability within southern hemisphere populations of the coccolithophore Emiliania huxleyi, we used eight microsatellite markers to conduct a population genetic analysis on 273 clonal cultures collected from 11 sites in five ocean current systems south of Australia (Leeuwin, Zeehan, East Australian Currents) and in the Southern Ocean, including within the Antarctic Polar Front. Two of the five currently recognised morphotypes were represented, E. huxleyi var. huxleyi and E. huxleyi var. aurorae. Clonality was absent within sampled populations, suggesting the importance of sexual reproduction in the life cycle of this coccolithophore. Significant genetic differentiation (pairwise population F ST range ¼ 0.01-0.09) was apparent among E. huxleyi var. huxleyi populations, much higher than for other cosmopolitan plankton species; thus, gene flow between populations must be low. There was evidence of marked differentiation between Southern Ocean populations of E. huxleyi var. aurorae and E. huxleyi var. huxleyi (pairwise F ST range ¼ 0.12-0.16), suggesting the existence of a reproductive, environmental and/or biogeographical barrier between these two varieties.
Marine Ecology Progress Series, 1980
Photosynthetic pigments in a warm core eddy of the East Australian Current were studied by In vjv... more Photosynthetic pigments in a warm core eddy of the East Australian Current were studied by In vjvo fluorometry, spectrophotometry and thin-layer chromatography. The Variosens i n sltu fluorometer gave only an approximate guide to the location and quantity of phytoplankton in the water column; spectrophotometric curve analysis revealed the presence of intact or detrital chlorophylls, and quantitative thin-layer chromatography showed that in some samples intact chlorophyll a accounted for only 50-70 % of the total spectrophotometrically measured 'chlorophyll' In addition the full range of chlorophylls, carotenoids and chlorophyll degradation products was recorded from the chromatograms.
Marine Ecology Progress Series, 1980
Summer phytoplankton populations in a warm core eddy of the East Australian Current were studied ... more Summer phytoplankton populations in a warm core eddy of the East Australian Current were studied by thin-layer chromatography for pigments and by microscopy of living samples for species identification. Small differences in phytoplankton populations at the eddy centre compared to surrounding waters were observed. These included higher subsurface chlorophyll maxima (0.49-0.89 pg 1-' eddy centre; 0.33-0.38 pg 1-' eddy edge; 0.27-0.34 yg I-' midway positions) due to increased diatom abundance, a lower proportion of nanoplankton chlorophyll (52 % eddy centre; 73 % eddy edge), a dominance change from Rhizosolenia alata (eddy edge) to Nitzschia seriata (eddy centre), and a decreased number of dinoflagellate species.
Marine Ecology Progress Series, 1987
Chlorophyllase activity, which degrades chlorophyll a to chlorophyhde a, was investigated in 93 s... more Chlorophyllase activity, which degrades chlorophyll a to chlorophyhde a, was investigated in 93 species (113 isolates) of unicellular algae from 10 classes. Chlorophyllide a formation was measured by a simple incubation test in 50 % acetone, followed by chromatography and phase separation techniques. High activity of the acetone-activated chlorophyllase was found in one third of the 68 diatom isolates tested. These included the pennate diatoms Asterionella glacialis, Cylindrotheca fusdormis, Delphinejs sp., Grammatophora oceanica, Navicda sp., Nitzschia (2 spp.), Phaeodactylum tncornutum and Thalassionerna nitzschioides, and the important bloom-forming centric d~atoms Chaetoceros (5 spp.), Detonula pumila, Ditylurn bnghtwellii, Eucampia zodiacus, Lithodesmium undulatum, Skeletonema costaturn, Stephanopyxis turris and Streptotheca tamesis. High activity was also found in 2 out of 3 chrysophyte isolates and 2 out of 7 chlorophyte isolates. In contrast, representatives of 7 other classes showed zero or low activ~ty: dinoflagellates (11 isolates), most prymnesiophytes (9 isolates), cryptophytes (5 isolates), prasinophytes (4 isolates), chloromonads (2 isolates), 1 rhodophyte and 2 cyanophytes. Significant strain-specific differences in chlorophyllase activity in 6 out of 13 diatom species, 1 chrysophyte, 1 prymnesiophyte and 1 chlorophyte were also observed. A serious problem for chlorophyll analysis is that chlorophyllase can be activated by harvesting techniques before extraction takes place. Filtration causes the most extensive conversion of chlorophyll a to chlorophyllide a, particularly in old cultures, but harvesting by centrifugation also causes chlorophyhde formation in some species. The effects are more pronounced in diatoms than other algal groups. The further degradabon of chlorophyllide a to pheophorbide a was seldom encountered. Whlle spectrophotometric and fluorimetric methods would not be seriously affected by chlorophyllase activity (provided pheophorbide a is a minor end product), TLC and HPLC techniques for chlorophylls may be rendered invalid due to artefact formation.
Deep Sea Research Part A. Oceanographic Research Papers, 1987
examined for phytoplankton species and pigments in autumn (April-May) 1981. During this period ph... more examined for phytoplankton species and pigments in autumn (April-May) 1981. During this period phytoplankton biomass (60-80 mg Chl a m 2) was higher at the eddy centre and western margin than at other stations inside and outside the eddy (20~0 mg Chl a m ~2). Nanoplankton plus picoplankton accounted for 60-70% of the chlorophyll at the eddy centre and western margin, and as much as 90% at some of the non-enriched stations. Light-penetration profiles (400-750 nm) distinguished eddy water with its increased phytoplankton biomass from tropical Coral Sea water from which the eddy was derived. Thin-layer chromatographic pigment analyses defined most algal types, confirmed the dominance of diatoms at high biomass sites and distinguished between pigments from living phytoplankton and detrital material. High proportions of detrital pigments were found in an "'old" submerged eddy system. Eddy centre and eddy margin enrichment processes resulted in blooms of the diatoms Nitzschia and Rhizosolenia, similar to those in the previously studied Eddy F (JEFFREY and HALLEGRAEFF, 1980a, Marine Ecology Progress Series, 3,285-294). Species differences between Eddy Mario and surrounding waters were minor, with 1 l0 out of a total of 160 species present both inside and outside the eddy. Tropical flora (e.g. Trichodesmium erythraeum, Richelia intracellularis and Scyphosphaera apsteinii) were found throughout the area as a result of flooding by water of tropical origin.
Verhandlungen, Oct 1, 1978
Marine Ecology Progress Series, 1999
Ten billion tonnes of shipping ballast water are carried around the world annually. This provides... more Ten billion tonnes of shipping ballast water are carried around the world annually. This provides a n inadvertant mechanism for the transfer and dispersal of harmful bacteria, toxic dinoflagellates, seaweeds, molluscs, starfish, crabs and fish (Rigby & Hallegraeff 1996). Establishment of nonindigenous and harmful organisms have resulted in significant ecological and environmental damage and also pose a threat to human health through Paralytic Shellfish Poisoning, and possibly even Cholera outbreaks (McCarthy & Khambaty 1994). As a result of these concerns, the International Mari-t~m e Organlsat~on has recogmsed shlpplng ballast wdter as an ~nternabonal pollutant of major consequence and 1s currently developmg a set of draft regulat~ons for potent~al use in future ~n t e r n a t~o n a l shlpplng operations These gu~dellncs will require ships to undertake appropriate management or treatment operations to minimise the risks of ballast water ~ntroductions. Ballast water exchange a t sea in organismdepleted deep ocean waters is currently the recommended treatment option, although this technique has some limitations (Rigby & Hallegraeff 1994). Here w e show how a novel, cost-effective heating technique using waste heat from the ship's main engine can be used to kill many unwanted organisms. Heated water flushed through 1 of the ballast tanks in an ocean trial resulted in destruction of all the zooplankton with very limited survival of the original phytoplankton. The original organisms were essentially reduced to flocculent amorphous detritus. KEY WORDS: S h i p p~n g ballast water. Ballast water treatment Ballast water management. Ballast water heatlng .
Phycologia, Mar 1, 1988
Some thirty Dinophysis species from Australian tropical and temperate, coastal and oceanic waters... more Some thirty Dinophysis species from Australian tropical and temperate, coastal and oceanic waters were examined by fluorescence and scanning electron microscopy, and eight selected species were also studied by transmission electron microscopy. The dinoflagellate genus ...
Harmful Algae, Jul 1, 2019
Blooms of the highly toxic dinoflagellate Alexandrium catenella (previously referred to as tamare... more Blooms of the highly toxic dinoflagellate Alexandrium catenella (previously referred to as tamarense group 1) were first detected off eastern Tasmania in 2012 and have since been responsible for incidences of human paralytic shellfish poisoning and extended closures (up to 25 weeks) of mussel, oyster, scallop, abalone and rock lobster industries (up to 150 mg/kg PST in mussels). Investigation of meteorological and oceanographic influences indicate that the annually recurrent winter-spring blooms (June-Oct) occur within a narrow water temperature window (10-15°C) under two distinct sets of conditions: (1) following high rainfall and land runoff , under relatively light winds; and (2) following periods of anomalously low air temperatures and associated cooling of shallow coastal waters, again under relatively light winds. The common driver of blooms appears to be the development of stratification in coastal waters, via salinity and/or temperature gradients. We propose a framework for evaluating the risk of Alexandrium with the aim of developing a forecasting capability, and compare these environmental conditions with historic data to understand the recent advent of these blooms.
UNESCO Publishing eBooks, 2003
Marine Ecology Progress Series, Jul 2, 2015
The invasion of anthropogenic carbon dioxide into the surface ocean is altering seawater carbonat... more The invasion of anthropogenic carbon dioxide into the surface ocean is altering seawater carbonate speciation, a process commonly called ocean acidification. The high latitude waters of the Southern Ocean are one of the primary and most severely affected regions. Coccolithophores are an important phytoplankton group, responsible for the majority of pelagic calcium carbonate production in the world's oceans, with a distribution that ranges from tropical to polar waters. Emiliania huxleyi is numerically the most abundant coccolithophore species and appears in several different ecotypes. We tested the effects of ocean acidification on 3 carefully selected E. huxleyi ecotypes isolated from the Southern Ocean. Their responses were measured in terms of growth, photosynthesis, calcification, cellular geometry, and stoichiometry. The 3 ecotypes exhibited differing sensitivities in regards to seawater carbonate chemistry when cultured at the same temperature (14°C) and continuous light (110 µmol photons m −2 s −1). Under future ocean acidification scenarios, particulate inorganic to organic carbon ratios (PIC:POC) decreased by 38−44, 47−51 and 71−98% in morphotype A 'over-calcified' (A o/c), A and B/C, respectively. All ecotypes reduced their rate of calcification, but the cold-water adapted ecotype (morphotype B/C) was by far the most sensitive, and almost ceased calcification at partial pressure of carbon dioxide (pCO 2) levels above 1000 µatm. We recommend that future surveys for E. huxleyi cells in the Southern Ocean should include the capability of recognising 'naked cells' by molecular and microscopic tools. The distinct differences in the physiological responses of these 3 dominant Southern Ocean coccolithophore ecotypes are likely to have consequences for future coccolithophore community structures and thereby the Southern Ocean carbon cycle.
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Papers by Gustaaf Hallegraeff